Various objects, including mineral resources such as iron ore and limestone, are conveyed by a conveyor belt. Those objects to be conveyed are fed onto the surface of an upper cover rubber of the conveyor belt from a hopper or from another conveyor belt. Here, for example, if the upper cover rubber is damaged by the object to be conveyed and a core layer, which bears the tension of the conveyor belt, is damaged as a result, the core layer becomes unable to sufficiently bear the tension. If the core layer is ruptured, the conveyor belt cannot be operated, and there is no choice but to discontinue the conveying operation. A significant amount of time and expense are required to repair or replace the ruptured conveyor belt and restore the operation. Thus, various technologies for detecting such failure of the conveyor belt at an early stage have been proposed (see Japanese Unexamined Patent Application Publication No. 2010-52927, for example).
However, the conventional methods proposed adopt a system in which elongation of the conveyor belt is monitored, and an abnormality is detected on the basis of the acquired elongation data. However, even when the elongation is significantly large, some conveyor belts (core layers) do not rupture easily. Further, the elongation of the conveyor belt is obtained as a total of an elongation of the core layer and a shift amount of an endless part (a connecting part) of the core layer. Thus, even when conveyor belts share identical specifications, variations occur in the elongation of the conveyor belt depending on a combination of the elongation and the shift amount. Therefore, in some cases, whether or not the conveyor belt is likely to rupture soon cannot be determined simply on the basis of the elongation of the conveyor belt. There has thus been room for improvement in relation to accurately detecting the signs of rupture and the like of the conveyor belt simply by monitoring the elongation of the conveyor belt.